Improvement of Carotenoids' Production by Increasing the Activity of Beta-Carotene Ketolase with Different Strategies.

ABSTRACT

Canthaxanthin is an important antioxidant with wide application prospects, and ß-carotene ketolase is the key enzyme involved in the biosynthesis of canthaxanthin. However, the challenge for the soluble expression of ß-carotene ketolase is that it hinders the large-scale production of carotenoids such as canthaxanthin and astaxanthin. Hence, this study employed several strategies aiming to improve the soluble expression of ß-carotene ketolase and its activity, including selecting optimal expression vectors, screening induction temperatures, adding soluble expression tags, and adding a molecular chaperone. Results showed that all these strategies can improve the soluble expression and activity of ß-carotene ketolase in Escherichia coli. In particular, the production of soluble ß-carotene ketolase was increased 8 times, with a commercial molecular chaperon of pG-KJE8, leading to a 1.16-fold enhancement in the canthaxanthin production from ß-carotene. Interestingly, pG-KJE8 could also enhance the soluble expression of ß-carotene ketolase derived from eukaryotic microalgae. Further research showed that the production of canthaxanthin and echinenone was significantly improved by as many as 30.77 times when the pG-KJE8 was added, indicating the molecular chaperone performed differently among different ß-carotene ketolase. This study not only laid a foundation for further research on the improvement of ß-carotene ketolase activity but also provided new ideas for the improvement of carotenoid production.